The present invention comprises a composition for melting ice and snow, and in particular provides a composition which includes a solid substrate coated with a liquid-phase melting compound.
An example of an ice-melting composition is provided in U.S. Pat. No. 4,597,884, the disclosure of which is incorporated by reference herein. The present invention comprises an improvement over the composition described in the above-cited patent.
As explained more fully in the above-cited patent, a major consideration in selecting a melting material is the corrosive effect the melting material will have on the surrounding environment. The cited patent uses urea, particularly prill urea particles, as the preferred melting material.
In the cited patent, it is recognized that urea still has disadvantages. Among these are the fact that urea is slow-acting, and is prone to being blown away before ice melting begins. It is also susceptible to refreezing. Moreover, when provided in the form of spherical particles, the degree of surface contact between the particles and the ice to be melted is limited, thereby limiting the effectiveness of the material for melting ice.
The cited patent therefore discloses urea particles which have been coated with a material provided in a liquid phase, wherein the liquid material helps to overcome the disadvantages of the urea. The preferred coating material is an antifreeze composition, which may be ethylene glycol or propylene glycol, and which may also include corrosion-inhibitors and wetting agents. In another embodiment, the coating material could be an aircraft deicing fluid.
The composition described in the above-cited patent works well, but has one environmental disadvantage, namely the production of nitrates and pollution of ground water sources. The urea itself is not a pollutant. However, when temperatures begin to rise in early spring, and the once-frozen ground becomes thawed, microbes become active, and secrete an enzyme that breaks down the urea into nitrates. These nitrates can migrate through the soil relatively quickly, and can eventually reach ground water sources. If sufficient quantities of nitrates reach the ground water, the result is a major pollution problem.
The present invention therefore provides an ice melting composition which has the advantages of the composition described in the above-cited patent, but which also reduces or eliminates the environmental hazard described above.